DESCRIPTION (revised by applicant): Sexual risk taking contributes directly to high rates of sexually transmitted disease and the continued spread of HIV infection. Despite many years of research, the mechanisms that lead to risk taking behavior are still poorly understood. Specifically, prior research has largely assumed that sexual decision-making depends on rational thought processes, and has not adequately addressed the role that emotional state plays in influencing behavior. This project will conduct systematic research on the mechanisms underlying the interrelationships among various types of positive or negative emotional state and sexual risk taking. In a series of studies, the individual and combined effects of positive or negative emotional state and interest on sexual risk taking will be examined. Individual differences in these relationships will be studied in men and women. A risk-taking paradigm is introduced that incorporates characteristics of established decision-making tasks while increasing ecological validity for sexual behavior. An additional objective of the research program involves the validation of a self-report measure (assessing the effects of emotional state on constructs related to sexual behavior) that could be used to identify and target relevant populations in future prevention and intervention programs.